Light pattern in all frames of STT-8300

Discussion in 'STT Series' started by Thomas Wincek, Mar 11, 2021.

  1. Thomas Wincek

    Thomas Wincek Standard User

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    Jul 10, 2016
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    My STT was working well until recently. I was taking some sky flats when I noticed a light pattern that I first thought may have been stray light entering the OTA. I acquired a few darks at 10 seconds at ambient temp and -20C and the pattern is still there. It is even present in the BIAS image.

    Here is a JPEG of the stretched bias:
    Bias -20.17C00015911.jpg

    Here is the 10 second dark stretched and saved as JPEG:
    Dark 10.000secs -20.17C00015910.jpg

    Thoughts? Thanks
     
  2. Doug

    Doug Staff Member

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    That is odd. Could you please post a FITS image?
     
  3. Thomas Wincek

    Thomas Wincek Standard User

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    Attached are the bias and dark in FITS
     

    Attached Files:

  4. Doug

    Doug Staff Member

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    If I take your bias frame and multiply it by 8, then subtract it from your dark frame (and add 100000 to every pixel so it doesn't go negative), it largely neutralizes the pattern. That and the shape of the pattern suggests to me that this is an optical effect.

    If it's not a light leak, then maybe it is the IR Preflash LEDs, which can be used to suppress RBI. If they're on (or just blink) when they're not supposed to be it might make this pattern.

    A few years back there was a change to the preflash controls, which could cause problems if you somehow ended up with incompatible software or drivers. So first thing to do:
    1. Download the latest SBIG Driver Checker ftp://ftp.sbig.com/pub/SetupDriverChecker64.exe (don't use the Update button in the driver checker - actually get the newest one because there have been improvements over the years)
    2. Use the driver checker to update your drivers
    3. Use the driver checker to update your camera firmware
    4. Now get the latest hot fix for TheSky and install that too
    After updating everything, see if that clears up the problem.
     
  5. Thomas Wincek

    Thomas Wincek Standard User

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    Thanks for all your efforts and suggestions. It took a while to me to discover this as the "pattern" calibrated out of my light frames as well. I will work thru your list of things to do.

    Regards, Tom
     

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